The petroleum industry is increasingly turning to heavy oil feeds such as heavy crudes, resids, coals, tar sands, etc. as sources for feedstocks. These feedstocks are characterized by high concentrations of asphaltene rich residues, and low API gravities, with some being as low as less than 0° API.
US Patent Publication No. 2008/0083650. US Patent Publication No. 2007/0138057. and U.S. Pat. No. 6,660,157 describe processes, systems, and catalysts for processing heavy oil feeds. In the prior art, a hydroprocessing unit typically comprises multiple reactors (or contacting zones) in series. A fresh catalyst (or regenerated catalyst) is fed into the first reactor with the heavy oil feedstock (untreated or treated, e.g., solvent deasphalted, thermally treated, etc.). Also in the prior art, the heavy oil feed enters the first (upstream) contacting zone. The unconverted oil, catalyst from the first reactor, and some make-up catalyst continues on to the next reactor in series until all the unconverted oil is converted to lower boiling point crude oils.
There is still a need for improved systems and methods to upgrade/treat process heavy oil feeds using novel feed schemes.